Method of drying dye impregnated fabrics



Aug. 9, 1966 A. MEIER-WINDHORST 3,264,748

METHOD OF DRYING DYE IMPREGNATED FABRICS Filed July 6, 1962 NW N 9 NR 2 v INVENTOR A. Meier -h/L'ndh r5t ATTORNEYS United States Patent Office Patented August 9, 1966 3 Claims. in. 34-12 This invention relates to a method and an apparatus for effecting the penetration, pre-drying and preliminary drying of woven materials and the like. The invention refers more particularly to .a process of drying fabrics, preferably fabrics which have been impregnated with solutions, emulsions, dispersions or thelike, as well as an apparatus for carrying out the process, more particularly a special drier for extended lengths of fabrics.

In prior art, after lengths of fabrics have been impregnated, dyed or otherwise saturated with a liquid, they are usually subjected directly after the saturation to a preliminary or final drying process with medium or high drying speeds. Often there is no certainty that there is the same concentration of the impregnating substance in the interior of the fabric as well as on its outer surface-s. When impregnation was properly carried out, however, the bath containing, for example, dye particles is uniformly distributed throughout all the fibers. If now the fabric or the fibers are subjected to a drying process, there is the possibility that the liquid will travel outwardly from the interior of the fibers and will carry the dye particles with it; this can happen particularly with dyes which have little :afiinity to the material of the fabric. Then the dye particles will collect close to the outer surfaces of the fabric. Thus the concentration of the dye is reduced in the interior of the fibers and is increased close to the outer surfaces of the fibers. A return movement of the dye particles from the outer surfaces inwardly is caused by the fact that the different concentrations within the fibers and at the'outer surfaces of the fibers tend to equalize. If there is still a great deal of liquid in the fibers the equalization of the concentration takes place faster than when there is little liquid. When the amount of humidity is less than about 30% the movement of the dye particles ceases completely.

When a fabric dyed in this manner is subjected to the usual high output drying, i.e., a drying by means of which the liquid is to be removed from the fibers as quickly as possible, which generally involves the use of very high temperatures, the dye particles which travel with the liquid outwardly from the interior of the fibers, will be collected close to the outer surfaces of the fibers and, since the drying has already progressed in that location, they can not move back into the interior of the fibers due to the equalization of concentration. Thus discoloration takes place in the interior of the fibers despite the fact that the fabric was initially thoroughly and well dyed, with the result that the quality of the fabric is diminished.

An object of the present invention is to eliminate the above described drawbacks.

Other objects will become apparent in the course of the following specification.

Investigations which were actually carried out, have shown that in order to assure a uniform distribution of dye particles in the fibers it is necessary, or at least most desirable, that the saturated fabric be initially exposed to a hum-id warm atmosphere so as to assure a quick and thorough impregnation or penetration and, furthermore, that it is advantageous during the first drying period, which is extended at the outer surfaces so .as to provide the return movement of the saturating substance, to maintain concentration, by somewhat increased temperatures of the materials, preferably in moist heat, but on the other hand to make certain that the drying speed is maintained below a predetermined very small amount during this phase of the drying procedures.

Thus in accordance with the present invention perfectly dyed goods are produced by a process of drying impregnated fabrics or the like, in accordance with which a fabric which, by way of example, was guided through a bath and then squeezed for the removal of excess water, is then subjected to the action of a humid warm atmosphere to assure a highly effective quick penetration, whereby no drying action or only very little drying takes place at the outer surfaces; immediately thereafter the fabric is subjected to a preliminary drying, which can be divided into individual zones, with initially small and then preferably increasing drying action, whereby the fabric is subjected to the high output drying only below the saturation point of the fibers. It is advantageous that the temperature differences between the drying temperature and the moist temperature of the steam-air mixture in the moist warm atmosphere and, preferably, in the beginning of the pre-drying period as well, be maintained quite low, namely, if possible, below 30 C. This can be assured, if necessary, by additionally spraying water into the regularly circulating medium, or by supplying steam. Through a corresponding regulation of these temperatures and of the heat transfer ratio between the medium and the length of fabric being treated, it is possible to lower the entire preliminary drying time to 1 to 2 minutes, which is a time period acceptable for industrial continuous production, whereby the highest quality of output is maintained. A penetration and drying process which is carried out in the described manner will produce substantially the same advantageous distribution of the treating medium throughout the cross-section of the material, as slow air drying.

An apparatus for carrying out the process of the present invention is characterized by a drier the interior of which is divided into several separated treating zones. The treating zones consist essentially of a penetration and predryin-g zone, as well as separate additional treating zones, such as a preliminary drying zone. In the penetration zone the treating medium for the fabric is preferably introduced and removed over perforated metal sheets located above and below the fabric. Nozzle fingers in counter type arrangement are advantageously provided in the pre-drying zone.

According to a preferred embodiment of the drier of the present invention, the fabric is. guided through the treating zones in the form of hanging loops, for example, by means of rod chains. To prevent an extension of the loops at the end of each path of the rod chains, reels or the like are provided for holding the loops at locations wherein the fabric is moved from one rod chain to the following one.

The invention will appear more clearly from the following detailed description when taken in connection with the accompanying drawing showing, by way of example, a preferred embodiment of the inventive idea.

The sole figure of the drawing illustrates in side view, partly in section, a drier constructed in accordance with the principles of the present invention.

The drawing shows a drier having a casing 10 which is mounted upon supports 22 and the outer walls of which are provided with insulation 21; by way of example, the drier is divided by a separating wall 23 into a treating chamber 11 and another treating chamber 12. Rod chains 13 run through the treating chambers and the fabric hangs upon them in smaller or longer loops depending upon the extent of drying, or the shrinkage connected therewith. Reels 14 which prevent an extension of the loops while the fabric is transmitted from one by wayof example, to 90%;

3 chain to another, are located at the ends of the rod chain paths.

The operation is as follows:

A length of fabric 16 which has been guided through a dye bath (not shown), is passed between rollers 15 constituting a squeezer wherein excess moisture in the fabric is removed, the remaining moisture amounting,

well known in the art is introduced into the drier through ablower 18. Finger-like nozzles (notshown) may .be arranged in counter type formation for introducing the treating medium into the pre-drying zone 12. Moisture in the treating medium should amount to about 80%.

Since a comparatively large amount of moisture isremoved along with the treating medium, the desired moisture content in the penetration zone of about:80%, may

be maintained, if necessary, by the spraying of water or by adding wet steam by any suitable means not shown in the drawing. The fabric may be guided above=and under perforated metal sheets '(not'shown). The fabric.16 passes through the chamber 11 during a time period of aobut 1 to 2 minutes. Under no circumstances should the fabric be allowed to remain in this zone of humid warm atmosphere longer than three minutes. At the end of the chamber 11 the fabric 16 is guided over rollers 17a and passes through an opening provided in a wall 23 which is located within the drier and which separates the upper chamber 11 from the lower chamber 12. The fabric thus reaches the lower treating chamber 12 which may be designated as the preliminary drying zone. In order to prevent the drying from taking place too quickly, which could impede the return movement of the. dye particles toward the interior of the fibers, the fabric can be moved several times back and forth through the preliminary drying zone. The temperature in the chamber 12 constituting the preliminary drying zone should amount 1 from about 60 C. to 90 C. and the moisture in the fabric should be reduced from initially about 80% to 30%, at most 25%. Rollers 17b and 170 are used to guide the fabric within the chamber 12. The treated fabric which has been dried until the fiber saturation point has been approximately reached leaves the drier through an opening 19 at the end of the pre-drying zone 12 having attained the drying range of from 45% to 55% and then can be moved to a high output drier (not shown) which will complete the dryingof the fabric to the.

desired final amount of moisture.

then the fabric passes over i The treating mediumwhich: was introduced into the drier through the blower 18, may leave the drier through a pipe 20: Throughout the specificationand claims the term"fiber saturation point is used todescribe the condition wherein the interior of the fibers is completely saturated with a liquid, 50 that the fibers cannot absorb any more liquid although s'there is no liquid upon the outer surfaces of the fibers. 7

It is apparent that the example; described above has been given solelyby Way of exemplificationzand not by way of limitation and that it is subjectto many variations and modifi'cationszwithin the scope of the present inven tion. All such variationsv and modificationsaare to vbe included within the: scope of the presentinvention. What is claimed is:

1..In a process of continuously treating lengths of dyed E textile fabrics,-in combination 'withia process of "impregnating a fabric ,with a dye solution andthen pressing,

excess moisture out of the impregnated fabric, the process Which=comprises the steps of thereupon maintaining the fabric for a predetermined time period in a moist and warm steam-containing atmosphere substantially with: out-drying the fabric, then preliminarily drying the fabric while .gradually increasing the, rate of :drying until the rangeof the fiber saturation point 'hasbeen reached, and

thereafter subjecting the fabric to aflnal outputdrying operation.-

2. "A process inaccordance with claim 1, wherein the difference between the temperatureof said moistand warm atmosphere and the temperatureat the beginning of the preliminary drying is less than 30 C.

3JA process in accordance with claim 1, comprising the additional step of spraying, an aqueous fluid to regulate the moisture content adjacent the fabric.v

References Cited by the Examiner UNITED STATES PATENTS 969,031 8/1910 Bratkowski 34-3l 1,886,030 11/1932 Lane 34-157' 1,903,325 4/1933 Colbert 34-157 2,059,441 11/:1936 Converse 3431 2,838,420 6/1958 Valente 34-23, 3,024,636 3/ 1962 Higginbottom 34-159,

FOREIGN PATENTS 877,618 12/1942i France- FREDERICK L: MATTESON, 111., Primary Examiner. NORMAN YUDKOFF, WILLIAM. F... ODEA,

Examiners.

W. C. EVERETT, D. A. TAMBURRO,

Assistant Examiners. 

1. IN A PROCESS OF CONTINUOUSLY TREATING LENGTHS OF DYED TEXTILE FABRICS, IN COMBINATION WITH A PROCESS OF IMPREGNATING A FABRIC WITH A DYE SOLUTION AND THEN PRESSING EXCESS MOISTURE OUT OF THE IMPREGNATED FABRIC, THE PROCESS WHICH COMPRISES THE STEPS OF THEREUPON MAINTAINING THE FABRIC FOR A PREDETERMINED TIME PERIOD IN A MOIST AND WARM STEAM-CONTAINING ATMOSPHERE SUBSTANTIALLY WITH- 